Protein-enriched whey fractions

ABSTRACT

Protein-enriched and lactose-enriched whey fractions are obtained by fine grinding dried whey in a pin or other impact milling device operated in the range of about 9,000 to 14,000 r.p.m. and then air classifying the fine ground whey into sized fractions in a standard air classifier.

United States Patent [191 Wolff et al.

1 PROTEIN-ENRICHED WHEY FRACTIONS [21] Appl. No.: 260,573

[52] US. Cl. 241/24, 241/27 [51] Int. Cl. B02c 13/14 [58] Field ofSearch 241/24, 27, 30, 68,

[56] References Cited 5 UNITED STATES PATENTS 2,867,387 1/1959 Dodds etal 241/188 A Jan. 8, 1974 3,640,475 2/1972 Jung et a1. 241/188 A PrimaryExaminer-Granvi11e Y. Custer, Jr. Attorney-R. Hoffman et al.

[57] ABSTRACT Protein-enriched and lactose-enriched whey fractions areobtained by fine grinding dried whey in a pin or other impact millingdevice operated in the range of about 9,000 to 14,000 r.p.m. and thenair classifying the fine ground whey into sized fractions in a standardair classifier.

2 Claims, No Drawings 1 PROTEIN-ENRICHED WHEY FRACTIONS A non-exclusiveirrevocable, royalty-free license in the invention herein described,throughout the world for all purposes of the United States Government,with the power to grant sublicenses for such purposes, is hereby grantedto the Government of the United States of America.

This invention relates to a process for separating dried whey intoprotein-enriched and lactose-enriched fractions and more particularly toa process in which fine grinding and air classification techniques areused to make such a separation.

Whey is an important by-product of the cheese manufacturing industry andalthough it contains valuable carbohydrate, protein and mineralconstituents less than 40 percent of the annual production in the UnitedStates is processed into human and animal food. Consequently, of themore than twenty billion pounds of whey produced in the United Stateseach year, an extremely large amount of it is discharged into streams orinto sewage and waste disposal systems where, because of its highbiological oxygen demand, it becomes a pollutant. In some areas wherestreams and waterways are overloaded with organic matter and sewagetreatment units are inadequate or expensive to construct and maintain,the problem of whey disposal has become so critical that some cheeseplants may be forced to discontinue operations.

Although many uses have been proposed, the utilization and disposal ofwhey is still a problem. By separating whey into fractions enriched inone or another of its components, better advantage can be taken ofnutritional or functional properties of specific components such asprotein. Thus, procedures such as electrodialysis, reverse osmosis,ultrafiltration, and selective crystallization of the lactose sugarcomponent have been suggested and applied to the preparation offractions having a higher percentage of a desired constituent than isfound in the parent material. However, for the most part, the proposedprocesses have been too costly.

An object of this invention is to provide a facile process forseparating dried whey into protein-enriched and lactose-enrichedfractions.

Another object of this invention is to provide a process of finegrinding and air classifying whey to obtain protein-enriched andlactose-enriched fractions.

in general, according to this invention the above objects areaccomplished by fine grinding dried whey in a pin mill or other impactmilling device at between about 9,000 and 14,000 r.p.m. and then airclassifying the fine ground whey into sized fractions in a standard airclassifier.

The separation of solid dry powdery natural materials such as wheatflour into protein-rich and protein-poor fractions by fine-grindingfollowed by a classification step such as classification in a controlledstream of air, is well known. The basis of such a separation is readilycomprehended since the flour is derived from a heterogeneous substance,the wheat grain or berry, by dry milling steps that result in a mixtureof particles with different character and composition.

One skilled in the art would not expect that similar types of separationcould be effected on a solid derived from evaporation to dryness ofsolution containing a mixture of substances. Contrariwise, he wouldexpect that the solid derived from such a solution would have thecomponent substances too homogeneously dispersed in one another fordifferences between solid particles to be amenable to separation by airor other means of classification. This was found to be true when anattempt was made to separate dry skimmilk by fine grinding and airclassification. The dry skimmilk could not be separated intoprotein-rich and protein-poor fractions.

Surprisingly, however, when a sample of commercially dried whey wassubjected to the same fine grinding and air classification process, itseparated into a protein-enriched portion and a protein-deficientportion. Although one may speculate as to why the dried whey separatedand the dried skimmilk did not, the reason for the separation is not yetknown.

Dried whey is derived from the manufacture of cottage and other types ofcheese. Whey from cottage cheese contains somewhat greater amounts ofacid than that from other types of cheese. However, the process of thisinvention can be used successfully on either type of whey.

Protein enrichment does not necessarily mean that the enriched fractionscontain protein as the predominant component but only that they aresignificantly richer in protein, by several percentage points, than thestarting material. It will be immediately apparent to those skilled inthe art that the process of this invention can be used in conjunctionwith or in tandem with other separation processes, and that one mayobtain a fraction containing a desired degree of protein enrichment by astepwise procedure in which one of the steps comprises the process ofthis invention, that is, the fine grinding of dried whey powder coupledwith air classification of the ground powder.

The invention is illustrated but not limited in scope by the followingexamples.

EXAMPLE 1- A commercial sweet whey product in the form of a dry powderwas used. It contained 15.8% of crude protein as determined in aconventional way by the Kjeldahl procedure for percentage nitrogen andmultiplying that nitrogen percentage by a factor of 6.38. The dried wheywas ground by one pass through a pin mill operated at 9,000 r.p.m. andthen air classified into five, sized fractions with a standard airclassifier. The protein-enriched fractions represented almost half thematerial and contained over twice as much protein as the remaining half,i.e., the coarse residue; 23.7 vs. 10.4 percent (initially 15.8 percentprotein, dry basis). The lactose showed a change of 21 percentage pointsbetween the extreme fractions with the coarse fraction (fraction 5, 56.8percent yield) containing 76.6 percent lactose. The data on this exampleshown in Table l.

Another sample of the commercial sweet whey product used in Example 1was treated as in Example 1 except that it was ground by a single passthrough a pin mill operated at 14,000 r.p.m. The results which differedonly slightly from those in Example 1 are shown in Table ll.

EXAMPLE 3 A commercial sample of nonfat dry milk was treated by theprocedure used in Example 1 The original sample contained 38% crudeprotein on a dry basis. There was no change in protein content for thevarious fractions. The nonfat dry milk did not separate intoprotein-enriched and protein-deficient fractions. This exampleillustrates that it would not be obvious to expect that a solid such asskimmilk or dried whey, derived ing negates the process. It alsoillustrates that simply grinding and air classifying will notnecessarily produce the desired results and that the process of thisinvention is not obvious from known prior art V 7 from evaporation todryness of a solution containing a TABLE m mixture of substances, couldbe separated into protein- Fraction YlCld Protein enriched andprotein-deficient fractions. Original whey 12.6 EXAMPLE 4 1 16.5 19.9 27.3 19.2 A commercially dried sweet whey powder was pro- 10 3 15.4 17.4

v cessed as described in Example 1. The results are 2 if: y: shown inTable 1L... L#

TABLE [V EXAMPLE 5 I '2 Qfggf "T Original whey no A commercially driedacid whey derived from the g f manufacture of cottage cheese wasprocessed as de- 3 scribed in Example 1. The results are shown in Table4 4, 5 37.3 e g 1v. w -L L We..-

TABLE 1 Yield Lactose Protein Ash Fat Moisture Fraction w.b.) db.) w.b.)w.b.)

Original 69.7 15.8 8.3 0.3 4.8 1... 10.7 56 23.7 11.7 0.5 7.8 2 5.7 5723.5 11.4 0.4 8.2 3 12.4 59 22.0 11.3 0.4 7.4 4... 14.4 62 19.3 9.9 0.37.3 5 b 56.8 77 10.4 5.8 0.2 5.8

Composite (cald) 15.3 8.0 0.3

Product recovery= 101% of feed (8.7 lbs.). 8 As percent of recoveredproducts. Fraction 5 is the coarse residue.

ABLE. .1.--.

Yield Lactose Protein Ash Fat Moisture Fraction w.b.) db.) w.b.) w.b.)

Composite (cald) 15.9 8.2 0.2

Product recovery= 99% of feed (8.6 lbs). 8 As percent of recoveredproducts. r q it 9a isust.-.

. TABLE! Yield Lactose Protein Ash Fat Moisture w.b.) d.b.) w.b.) w.b.)

Fractions 1 and c 39.1 74 12.9 8.2 0.4 8.8 Fractions 3 and c 49.3 12.98.6 0.3 8.9 Fraction 11.6 69 12.9 8.7 0.3 9.8 Composite (cald) Productrecovery 100% of feed (3.0 lbs.).

DEHSEEPDEQUL We claim: 1. A process for the preparation ofprotein-enriched and lactose-enriched fractions from dried wheycomprising fine grinding said dried whey in an impact type millingdevice operated at a speed in the range of about 9,000 to 14,000 rpm.and air classifying said ground dried whey.

2. The process of claim 1 in which the impact type milling device is apin mill.

2. The process of claim 1 in which the impact type milling device is apin mill.